Technical Field
Embodiments of the subject matter disclosed herein relate to adjusting operation of an engine.
Discussion of Art
Turbocharging an engine allows the engine to provide power similar to that of a larger displacement engine. Thus, turbocharging can extend the operating region of an engine. Turbochargers function by compressing intake air in a compressor driven by a turbine operated by exhaust gas flow. The turbine may include a turbine bypass valve arranged in a bypass passage around the turbine. As such, the turbine bypass valve may be adjusted to divert exhaust flow around the turbine, thereby decreasing boost provided by the compressor. Under certain conditions, decreased boost may be requested. In one example, the turbine bypass valve may be adjusted to maintain a plurality of engine operating conditions below a set of upper operating limits. For example, the turbine bypass valve may be adjusted in order to maintain turbine speed, peak cylinder pressure, and a pressure difference across the turbine below corresponding upper operating limits in order to reduce engine component degradation. However, adjusting the turbine bypass valve based on multiple variables relative to multiple upper limits may increase the control complexity of controlling the turbine bypass valve.